Charles e



(No Model.) w

G. E. SGRIBNER, TE ST CIRCUIT FOR MULTIPLE SWITGHBOARDS.

No. 502,768. Patented An us, 1893 I 205572619508 AYMBZOV072 UNITED; STATES PATENT OFFICE...

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNQR TO" THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

TEST-CIRCU IT FOR M U LT'I PLE SWIT CHBOAR DLS.

'SPEOIFIGATION forming part of Letters Patent No. 502,768, dated August 8, 1893.

Application filed December 27,1886. Serial No. 222,701. (No model.)

multiple switch board systems, and its obj ect is to enable the operator at one board to determine whether a line called for is in use at any other board. The circuits are so arranged that connection may be' made from any spring jack to line without including in the circuit the contact points of the different spring jack switches of the line. Y My invention herein is an improvement upon the system of test circuits shown in my Patent No. 305,021, of September 9, 1884.

My invention consists in permanently con necting the test circuit of each line to its line and in providing switching apparatus where by after connection is madewith the insu; lated frameor portion of the spring jack, the connection of the branch of the line extend ing to the springs or lovers of the spring jacks will be broken." This breaking of ,the branch of the circuit will cause a click in the telephone connected in circuit with a battery This click will be with the insulated frame. a signal that the line is free. If, however, a connection is already formed at any other of the spring jacks of the line, another break Figure 1 shows two telephone lines and their test circuits connected with spring jack switches upon two different multiple switch boards and the operators outfit at each of nection f that I have added to each circuit.

The connecting plugs are provided with me tallic shanks. Thus, as shown'in Fig. 2, the cord connects with the metallic shank of the plug and the tip 9 is of hardrubber or other insulating'material. Whenrno plug is inserted in any switch of a line, a circuit may be traced from the frame of any one of the switches by branch f tothe line and thence through all the switches of the line and the annunciator to ground. Thus,normal1y, when a line is not in use, a continuous circuit may be traced from the frame of any spring jack through the contacts of all the spring jacks of the line and the individual annunciator to ground. Circuit may also be traced by the line to the subscribers station and to ground in the usual manner. It is, however, by determining whether the circuit from the frame of any given spring jack is continuous through all the spring jacks and'to ground that the operator testing at the spring jack is enabled to determine whether the line is in use. If the circuit is continuous, he will know that the line is free. If broken, he will infer that the line is connected at some of the other spring jacks.

'A telephone and battery maybe looped in the circuit of each pair of cords by means of the loop key shown, or by any other suitable switch. When one plug of a pair is lifted and inserted in a spring jack, connection is made between the frame of the spring jack and the metallic shank of the plug, and then, as the plug is forced farther in, the rubber tip wedges the spring away from its contact point, thus breaking the circuit between the spring and said contact point. As, however, the wire 6 is connected to line, a circuit will be formed which may be traced from the ground at the subscribers station over the line in the usual manner, and thence, as shown, by branch f to the frame of the switch in which the plug is inserted, and thence to the shank of the plug and thence to the cord and thence through the pair of cords and the telephone and battery included in circuit therewith, to the other plug of the pair, and when said plug is resting on its ground plate, from said plug to ground. When, however, the other plug of the pair is inserted in any spring jack, the circuit will be traced to the line of the other spring jack and over said line to ground at the other subscribers station.

We will suppose that the operator at the second board wishes to test to determine whether line (1V is busy. He will take up one of his plugs-we will say plug hand insert said plug in the switch of said line a. The shank of said plug it coming against the frame cl will first close the circuit of the cords to said frame and afterward, as the plug is inserted farther and the spring is lifted, a break will be made between said spring and its contact point. Now, when said break is made, if no other break exists in the line, the operator listening at his telephone included in the circuit, will hear a click. If, however, the portion of the circuit including the spring jacks of the line is broken at any other of the spring jacks of the line, another break will cause no variation in the strength of the current passing through the telephone and hence there will be no click, and the operator will know that the line is busy.

When an operator plugs into the springjack of a line called for, the metallic shank will, in all cases, come in contact with the metallic frame or tube of the springjack, and upon the making of this contact a click will be heard in the operators telephone. This click will be heard, no matter whether the line be in use or free. The plug, however, on being inserted farther, lifts the spring of the springjack from its contact, thus breaking the circuit of the portion of the line which connects through the springs of the springjacks and the annnnciator of the line to ground. This break will produce another click in the operators telephone if the line be not in use, as it will open a ground circuit connected with the operators telephone. If, however, the line be in use, this ground circuit will have been already opened at the springjack on another board where the connection has been made. Therefore there will be no second click in the telephone if the line is busy; that is to say, two clicks in succession indicate that the line is free; one click only heard in the telephone indicates that the line is busy.

Having thus described my invention, I

claim as new and desire to secure by Letters Patent- 1. In a multiple switch board system of telephone exchange, a telephone line perinanently connected with the insulated frames of spring jack switches, one on each of the boards, and the circuit from said line through 1 portion of the circuit including the springs of the switches; whereby it may be determined whether the line is in use or connected at any of the other boards.

2. In a multiple switch board system, the combination of spring jack switches, one switch on each of the multiple boards, connections from the subscribers line to the frame of each spring jack switch, a branch circuit through the springs and contact points of the jacks to ground, the operators telephone circuit including battery and switching apparatus for connecting the telepone circuit to the line and breaking the branch circuit to ground; whereby the operator can determine whether a line has been previously connected at any other board.

3. In a multiple switchboard system the combination with telephone lines each extending to all the switchboards, of springjack switches, one switch on each of the multiple boards for each of the telephone lines, connections from each subscribers line to the frame of the springjack switches of the line, a branch circuitthrough the springs and contact pointsof the springjack switches of each line to ground, the operators telephone circuit including battery at each of the boards and a plug and its cord connected with a telephone at each board, the plugs being provided with a tip of insulating material and a metallic shank whereby, on inserting the plug in any switch upon either of the boards, the operator listening at the telephone may determine Whether or not the line of the springjack with which connection is made is 1n use.

4:. A line connected with two or more switches on dilferent boards, a branch of the line being connected with normally open contact pieces of the springjack, another branch of the line being connected through the circuit closing portion of each springjack to ground, a test plugconnected to a telephone and test battery to ground, said test plug being constructed to first make contact with the normally open contact piece of the springjack and immediately thereafter to break the circuit of the branch to ground; whereby the operator may determine on inserting a plug into any springjack switch of a line whether the line is or is not in use. I

5 A telephone line branched to two por:

IIO

tions of several springjacks, one branch connecting with the frames of the several springjacks, the other branch connecting through the circuit closing springs of said springjacks and to ground, a test plug connecting with a telephone and battery to ground, the said test plug being provided with a metallic shank to make contact with the frame of the springjack, and a tip of insulating material to lift the circuit closing spring of the springjack; whereby an operator may determine whether the branch circuit through the springjacks to ground is completed, to tell whether a line is in use.

6. A telephone line extending from a subscribers station to a central oflice, said line extending in one branch to the insulated frames or test pieces of springjack switches,

one on each of the boards, and another branch of said line extending through the spring and contact of said switches to ground, in combination with a test plug connecting with a telephone and battery to ground, said plug being provided with a metallic portion, and a portion of insulating material; whereby, on inserting the plug in any springjack of the line, the operator listening at the telephone may determine whether the line is connected or in use at any other of the boards.

In witness whereof I hereunto subscribe my name this 16th day of November, A. D. 1886.

OHARI JES E. SCRIBNER.

Witnesses:

GEORGE P. BARTON, WM. M. GILLER. 

